Coupling devices, such as ball and socket coupling devices, can be used to connect a variety of objects, such as for example trailers to vehicles. The ball and socket connection permits relative movement between the trailer and the vehicle via rotation or pivoting of the ball within the socket. A traditional trailer hitch has the ball mounted to a hitch plate or rear bumper of the vehicle with the shank of the vehicle coupling member extending upwardly and having a ball formed at the upper end thereof, and the socket is mounted to a tongue of the trailer and has its opening facing downwardly. To couple the trailer to a hitch, the trailer tongue is first lifted up above the ball in order to align the trailer socket with the ball on the vehicle before the socket is lowered downwardly onto the ball. Once the ball is seated within the socket, locking elements or detent balls keep the ball and socket connected during operation of the powered vehicle.
One typical type of prior ball and socket coupling device utilizes a locking mechanism comprised of a ring or sleeve that is connected to the socket. In these devices, movement of the ring or sleeve shifts detent balls in the socket to engage or disengage the ball when the ball is seated within the socket. Though this approach permits relatively straightforward operation, these coupling devices suffer from a number of shortcomings.
One such problem is that existing coupling devices have a configuration that may allow debris or contamination from the surrounding environment to foul the ball. For example, in U.S. Pat. No. 2,696,392 to R. N. Case and U.S. Pat. No. 2,755,105 to Wells, ball and socket devices are described each including a body having a downwardly opening, spherical recess or socket connected to a trailer tongue and a coupling ball on the upper end of a shank connected to and extending upwardly from a car bumper for being received within the spherical recess of the body. The socket body has radial through passages extending through the wall of the socket body for receiving detent balls therein. These passages are configured to permit the ball bearings to translate and partially extend into the recess to lock the ball in the socket. Slideably mounted on the body is a ring or sleeve that is biased in a direction toward an access opening of the socket to a locked position and which is slideable in an opposite direction against the bias force away from the opening of the socket to an unlocked position where the detent balls can travel radially outward to allow the coupling ball to be seated within the socket. Releasing the sleeve causes it to shift back toward the socket opening to its locked position which locks the device by forcing the detent balls radially inward to extend partially into the socket, which secures the ball within the socket. However, sliding the sleeve away from the socket access opening to the unlocked position exposes the radial passages and detent balls therein to fouling from the surrounding environment. The exposure provides debris or other contaminants access to the passages. Additionally, if the sleeve is shifted too far away from the opening of the socket because the spring is worn, damaged, or overextended, the detent balls can actually fall out of the socket.
Another problem with existing coupling devices is due to the use of a coil spring for biasing the sleeve or ring to the locked position. In the '105 patent, sliding the ring away from the cup access opening compresses the coil spring and permits the detent balls to shift radially outwardly such that the spherical head may be inserted into or removed from the cup. The ring can be slid away from the cup access opening until the adjacent coils of the spring engage one another causing the coil spring to bottom-out. Such bottoming out of the spring provides a hard stop of the ring slid to the unlocked position thereof. However, fully compressing the spring every time the spherical head is inserted or removed from the cup repeatedly exposes the spring to excessive wear and tear and possible risk of deformation. This shortcoming may lead to spring failure or a reduced capacity of the spring to return the ring to its locked position.
Prior ball and socket coupling devices also pose additional problems with respect to the difficulty involved with connecting the ball to the socket. Specifically, the socket is connected to a trailer tongue to open downwardly and the ball is connected to a vehicle hitch plate via an upwardly projecting shank on which the ball is formed. The weight of the trailer tends to shift the trailer tongue downwardly, which moves the trailer socket downwardly onto the ball. With this hitch configuration as also shown by Wells and Case, to unlock the socket, the sleeve or ring on the trailer mounted socket is pulled back upwardly and away from the socket access opening and, thus, is shifted in an opposite direction of the natural downward movement of the trailer socket as it is lowered to receive the ball therewith. Thus, to seat the ball in the socket, a user has the difficult operation of pulling the ring or sleeve upwardly or away from the socket access opening while at the same time the trailer tongue and socket must be lowered downwardly in the opposite direction to seat the vehicle mounted coupling ball. In addition, the socket is often larger than the ball and when positioned over the ball and vehicle hitch plate, the large socket tends to visually obscure the ball when the user is aligning the ball and socket. Even once the socket is positioned onto the ball, existing devices further impede coupling by utilizing locking mechanisms that require pulling a ring in a direction which tends to separate the ball and socket.
Prior ball and socket devices also have the shortcoming that excessive force can, under some circumstances, shift the socket or ring to a position where the detent balls are released and the ball pin can be unintentionally unlocked from the socket resulting in locking failure. Such locking failure can occur when significant axial forces are created by abrupt changes in the orientation of the ball and socket devices. For example, a coupled ball and socket device between a vehicle and a trailer being transported through high-speed pothole collisions, abrupt bumps or other changes in the terrain, jerky motions due to driving conditions, or failure in the item being pulled, can experience significant axial forces that can overcome the bias of the socket ring resulting in locking failure. One attempt to overcome this problem would be to install a much heavier biasing member on the locking ring to provide a much larger biasing force to maintain the ring in the locked position. This solution, however, would greatly deter the ease of use of the ball and socket device because a much higher force would be needed by an operator to counter-bias the locking ring in order to unlock the device.